A mushroom extract boosted a type of white blood cell (dendritic) that helps the immune system kill and remember foreign substances. Scientists in this study gave 21 healthy volunteers 3 grams per day of mushroom extract—active hexose correlated compound (AHCC)—or a placebo. After four weeks, dendritic cell levels were significantly higher in the AHCC group compared to the start of the study and compared to the placebo group. Study authors said, “Dendritic cells are critical for maintaining a healthy and balanced immune system.”

In a review of vitamin C and zinc in the Annals of Nutrition & Metabolism, researchers noted a large number of placebo-controlled studies show that vitamin C combined with zinc—up to 1 gram and 30 mg per day, respectively—“…ameliorates symptoms and shortens the duration of respiratory tract infections including the common cold.” Both vitamin C and zinc boost immune-system “killer” cells.

In a study on zinc, doctors noted that adults over age 55 are often low in zinc, have poor immune response and are prone to infection. Scientists first compared zinc levels of the 50 healthy participants, aged 55 to 87, to a group of healthy younger adults (non-participants) and found that the older group had significantly lower zinc levels. Participants then took 45 mg of zinc gluconate per day or a placebo. After 12 months, there were 80 percent fewer total infections in the zinc group compared to placebo and no sign of infection in 68 percent of the zinc group compared to 12 percent for placebo. Infections included the common cold, tonsillitis and bronchitis. The zinc group also had significantly less cell damage (oxidation) and significantly fewer signs of inflammation compared to placebo.

Bronchitis inflames the airways to the lungs, causing a severe cough that can last up to a month. In this study, doctors noted that bronchitis is usually viral and that antibiotics—which fight bacteria, not viruses—often don’t relieve symptoms or shorten duration. Researchers recruited 124 men and women with acute bronchitis, average age 36, to take 4.5 mg (30 drops) of the African herb Umcka (Pelargonium sidoides) three times per day, 30 minutes before or after meals. After seven days, 85 percent of those who took Umcka had completely or mostly recovered compared to 30 percent for placebo.

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